To make the pickle, heat the vinegar, sugar and salt in a small pan. Boil for 1 min until the sugar dissolves, then add the red onion and simmer for 1 min. Take off the heat, cover, and leave to cool completely.
Mix the broccoli, carrots, cranberries and cashews in a large bowl. Add the cooled pickled onion, reserving the pickling liquid.
Whisk together the pickling liquid, oil, maple syrup and lemon zest and juice, along with 2 tbsp cold water. Pour over the vegetables and mix until well coated.
